The Dell Poweredge R420 chassis comes with a cabled power supply option and a redundant hot swappable power supply option. The spare power supplies come in Platinum efficiency 550W and 350W (for one processor only) power supplies Silver efficiency cabled 550W power supply, auto-ranging power supplies options. Make sure you are replacing or adding an additional power supply that matches the wattage of the current power supply installed. Always replace with a genuine Dell power supply specifically engineered for the Dell Poweredge R420.
If you are receiving the error message Dell Poweredge R420 power required exceeds PSU wattage you should look at installing the largest wattage power supplies. If you are currently using the largest wattage Poweredge R420 power supply you will want to try replacing them. One of the power supplies could be causing the Poweredge R420 to have a wattage error.
If we are not showing stock contact us at 952-831-1032 as we most likely have in servers that we can pull the power supply from.